Omid Kavehei

Memristor MOS Content Addressable Memory (MCAM): Hybrid Architecture for Future High Performance Search Engines

Large-capacity content addressable memory (CAM) is a key element in a wide variety of applications. The inevitable complexities of scaling MOS transistors introduce a major challenge in the realization of such systems. Convergence of disparate technologies, which are compatible with CMOS processing, may allow extension of Moores Law for a few more years. This paper provides a new approach towards the design and modeling of Memory resistor (Memristor)-based CAM (MCAM) using a combination of memristor MOS devices to form the core of a memory/compare logic cell that forms the building block of the CAM architecture. The non-volatile characteristic and the nanoscale geometry together with compatibility of the memristor with CMOS processing technology increases the packing density, provides for new approaches towards power management through disabling CAM blocks without loss of stored data, reduces power dissipation, and has scope for speed improvement as the technology matures.

The fourth element: characteristics, modelling and electromagnetic theory of the memristor

In 2008, researchers at the Hewlett–Packard (HP) laboratories published a paper in Nature reporting the development of a new basic circuit element that completes the missing link between charge and flux linkage, which was postulated by Chua in 1971 (Chua 1971 IEEE Trans. Circuit Theory 18, 507–519 (doi:10.1109/TCT.1971.1083337)). The HP memristor is based on a nanometre scale TiO2 thin film, containing a— doped region and an undoped region. Further to proposed applications of memristors in artificial biological systems and non-volatile RAM, they also enable reconfigurable nanoelectronics. Moreover, memristors provide new paradigms in application-specific integrated circuits and field programmable gate arrays. A significant reduction in area with an unprecedented memory capacity and device density are the potential advantages of memristors for integrated circuits. This work reviews the memristor and provides mathematical and SPICE models for memristors. Insight into the memristor device is given via recalling the quasi-static expansion of Maxwell’s equations. We also review Chua’s arguments based on electromagnetic theory.

A novel design for quantum-dot cellular automata cells and full adders

Quantum-dot Cellular Automata (QCA) is a novel and potentially attractive technology for implementing computing architectures at the nano-scale. The basic Boolean primitive in QCA is the majority gate. In this study we present a novel design for QCA cells and another possible and unconventional scheme for majority gates. By applying these items, the hardware requirements for a QCA design can be reduced and circuits can be simpler in level and gate counts. As an example, a one bit QCA adder is constructed by applying our new scheme. Beside, we prove that how our reduction method decreases gate counts and levels in comparison to the other previous methods.

Efficient Reverse Converter Designs for the New 4-Moduli Sets

In this paper, we introduce two new 4-moduli sets {2ⁿ-1, 2ⁿ, 2ⁿ+1, 2²ⁿ⁺¹-1} and {2ⁿ-1, 2ⁿ+1, 2²ⁿ, 2²ⁿ+1} for developing efficient large dynamic range (DR) residue number systems (RNS). These moduli sets consist of simple and well-formed moduli which can result in efficient implementation of the reverse converter as well as internal RNS arithmetic circuits. The moduli set {2ⁿ-1, 2ⁿ, 2ⁿ+1, 2²ⁿ⁺¹-1} has 5<i>n</i>-bit DR and it can result in a fast RNS arithmetic unit, while the 6<i>n</i>-bit DR moduli set {2ⁿ-1, 2ⁿ+1, 2²ⁿ, 2²ⁿ+1} is a conversion friendly moduli set which can lead to a high-speed and low-cost reverse converter design. Next, efficient reverse converters for the proposed moduli sets based on new Chinese remainder theorems (New CRTs) are presented. The converter for the moduli set {2ⁿ-1, 2ⁿ, 2ⁿ+1, 2²ⁿ⁺¹-1} is derived by New CRT-II with better performance compared to the reverse converter for the latest introduced 5 <i>n</i>-bit DR moduli set {2ⁿ-1, 2ⁿ, 2ⁿ+1, 2^n-1-1, 2ⁿ⁺¹-1}. Also, New CRT-I is used to achieve a high-performance reverse converter for the moduli set {2ⁿ-1, 2ⁿ+1, 2²ⁿ, 2²ⁿ+1}. This converter has less conversion delay and lower hardware requirements than the reverse converter for a recently suggested 6<i>n</i>-bit DR moduli set {2ⁿ-1, 2ⁿ+1, 2²ⁿ-2, 2²ⁿ⁺¹-3} .

\{2^{n} -1, 2^{n}, 2^{n} +1, 2^{2n + 1}-1\}

In this paper a new low power and high performance adder cell using a new design style called “Bridge” is proposed. The bridge design style enjoys a high degree of regularity, higher density than conventional CMOS design style as well as lower power consumption, by using some transistors, named bridge transistors. Simulation results illustrate the superiority of the resulting proposed adder against conventional CMOS 1-bit full-adder in terms of power, delay and PDP. We have performed simulations using HSPICE in a 90 nanometer (nm) standard CMOS technology at room temperature; with supply voltage variation from 0.65v to 1.5v with 0.05v steps.

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The nonvolatile memory property of a memristor enables the realization of new methods for a variety of computational engines ranging from innovative memristive-based neuromorphic circuitry through to advanced memory applications. The nanometer-scale feature of the device creates a new opportunity for realization of innovative circuits that in some cases are not possible or have inefficient realization in the present and established design domain. The nature of the boundary, the complexity of the ionic transport and tunneling mechanism, and the nanoscale feature of the memristor introduces challenges in modeling, characterization, and simulation of future circuits and systems. Here, a deeper insight is gained in understanding the device operation, leading to the development of practical models that can be implemented in current computer-aided design (CAD) tools.

\{2^{n} -1, 2^{n} +1, 2^{2n}, 2^{2n} +1\}

This paper presents a novel low-power majority function-based 1-bit full adder that uses MOS capacitors (MOSCAP) in its structure. It can work reliably at low supply voltage. In this design, the time-consuming XOR gates are eliminated. The circuits being studied are optimized for energy efficiency at 0.18-@mm CMOS process technology. The adder cell is compared with seven widely used adders based on power consumption, speed, power-delay product (PDP) and area efficiency. Intensive simulation runs on a Cadence environment and HSPICE show that the new adder has more than 11% in power savings over a conventional 28-transistor CMOS adder. In addition, it consumes 30% less power than transmission function adder (TFA) and is 1.11 times faster.

Based on New CRTs

As conventional memory technologies are challenged by their technological physical limits, emerging technologies driven by novel materials are becoming an attractive option for future memory architectures. Among these technologies, Resistive Memories (ReRAM) created new possibilities because of their nanofeatures and unique I-V characteristics. One particular problem that limits the maximum array size is interference from neighboring cells due to sneak-path currents. A possible device level solution to address this issue is to implement a memory array using complementary resistive switches (CRS). Although the storage mechanism for a CRS is fundamentally different from what has been reported for memristors (low and high resistances), a CRS is simply formed by two series bipolar memristors with opposing polarities. In this paper, our intention is to introduce modeling principles that have been previously verified through measurements and extend the simulation principles based on memristors to CRS devices and, hence, provide an analytical approach to the design of a CRS array. The presented approach creates the necessary design methodology platform that will assist designers in implementation of CRS devices in future systems.

Low-Power and High-Performance 1-Bit CMOS Full-Adder Cell

Physical unclonable functions (PUFs) exploit the intrinsic complexity and irreproducibility of physical systems to generate secret information. The advantage is that PUFs have the potential to provide fundamentally higher security than traditional cryptographic methods by preventing the cloning of devices and the extraction of secret keys. Most PUF designs focus on exploiting process variations in Complementary Metal Oxide Semiconductor (CMOS) technology. In recent years, progress in nanoelectronic devices such as memristors has demonstrated the prevalence of process variations in scaling electronics down to the nano region. In this paper, we exploit the extremely large information density available in nanocrossbar architectures and the significant resistance variations of memristors to develop an on-chip memristive device based strong PUF (mrSPUF). Our novel architecture demonstrates desirable characteristics of PUFs, including uniqueness, reliability, and large number of challenge-response pairs (CRPs) and desirable characteristics of strong PUFs. More significantly, in contrast to most existing PUFs, our PUF can act as a reconfigurable PUF (rPUF) without additional hardware and is of benefit to applications needing revocation or update of secure key information.

Memristive Device Fundamentals and Modeling: Applications to Circuits and Systems Simulation

Novel direct designs for 3-input exclusive-OR (XOR) function at transistor level are proposed in this article. These designs are appropriate for low-power and high-speed applications. The critical path of the presented designs consists of only two pass-transistors, which causes low propagation delay. Neither complementary inputs, nor V DD and ground exist in the basic structure of these designs. The proposed designs have low dynamic and short-circuit power consumptions and their internal nodes dissipate negligible leakage power, which leads to low average power consumption. Some effective approaches are presented for improving the performance, voltage levels, and the driving capability and lowering the number of transistors of the basic structure of the designs. All of the proposed designs and several classical and state-of-the-art 3-input XOR circuits are simulated in a realistic condition using HSPICE with 90 nm CMOS technology at six supply voltages, ranging from 1.3 V down to 0.8 V. The simulation results demonstrate that the proposed circuits are superior in terms of speed, power consumption and power-delay product (PDP) with respect to other designs.